add kms:GenerateRandom and tests

moto/kms/responses.py

@@ -2,7 +2,9 @@ from __future__ import unicode_literals
 
 import base64
 import json
+import os
 import re
+
 import six
 
 from moto.core.responses import BaseResponse
@@ -384,6 +386,15 @@ class KmsResponse(BaseResponse):
 
         return json.dumps(result)
 
+    def generate_random(self):
+        number_of_bytes = self.parameters.get("NumberOfBytes")
+
+        entropy = os.urandom(number_of_bytes)
+
+        response_entropy = base64.b64encode(entropy).decode("utf-8")
+
+        return json.dumps({"Plaintext": response_entropy})
+
 
 def _assert_valid_key_id(key_id):
     if not re.match(r'^[A-F0-9]{8}-[A-F0-9]{4}-[A-F0-9]{4}-[A-F0-9]{4}-[A-F0-9]{12}$', key_id, re.IGNORECASE):

tests/test_kms/test_kms.py

@@ -908,6 +908,21 @@ def test_re_encrypt_to_invalid_destination():
         )
 
 
+@parameterized(((12,), (44,), (91,)))
+@mock_kms
+def test_generate_random(number_of_bytes):
+    client = boto3.client("kms", region_name="us-west-2")
+
+    response = client.generate_random(NumberOfBytes=number_of_bytes)
+
+    # Plaintext must NOT be base64-encoded
+    with assert_raises(Exception):
+        base64.b64decode(response["Plaintext"], validate=True)
+
+    response["Plaintext"].should.be.a(bytes)
+    len(response["Plaintext"]).should.equal(number_of_bytes)
+
+
 @mock_kms
 def test_enable_key_rotation_key_not_found():
     client = boto3.client("kms", region_name="us-east-1")